Gallium nitride based high power-density automotive HID electronic ballast

Owing to the development of wide bandgap power semiconductors, the emergence of gallium nitride (GaN) power transistors offers the possibility to acquire higher efficiency and switching frequencies as compared to Si MOSFETs. Constraints in circuit characteristics, packaging and layout parasitic should be taken special care to achieve best performance of power devices. This paper explores the application of GaN devices in the design of automotive HID electronic ballast with planar magnetic components. The parasitic ringing and switch immunity caused by parasitic impacts, which have great effect on the property of GaN based HID ballast, are analyzed. In power converters with paralleled GaN switches, this effect is more significant. To minimize negative parasitic effects, design considerations of circuit and layout are proposed. In addition, the maximal length of gate driving loop is calculated theoretically. The validity of the design and analysis is confirmed experimentally with 35W full digital controlled prototype. Experimental results show that GaN based electronic ballast could ignite and operate HID lamps successfully. A performance comparison of platforms respectively based on commercially available GaN and Si power devices, verifies that utilizing GaN transistors with recommended design will increase the efficiency notably, as well as its power density.